In order for a tire sensor monitoring system to know when to alert the user that the sensor reading is at a critical level, one or more baseline values must be provided. For example, a baseline tire pressure of 100 pounds per square inch (psi), with a variance of plus or minus 5 psi may be suitable for truck tires. If the sensor on a tire transmits a signal indicating that the actual pressure is 75 psi, the processor in the monitor will compare the actual sensor value with the baseline value. Since the disparity between 75 psi and 100 psi is substantial, the monitor may, in addition to displaying the actual reading, activate an audible and/or visual warning.
Typically, the monitor that displays the tire sensor information is equipped with keys, arrows or a touch screen for entering data. In the past, baseline pressure/temperature values were entered on a tire-by-tire basis. Since a standard North American tractor trailer has 18 tires in contact with the road, entering the baseline parameters was a time-consuming task. If the vehicle included a second semi-trailer, the input process was even longer.